A magnetic resonance imaging apparatus is an apparatus that applies a radio-frequency magnetic field onto a subject placed in a static magnetic field, and detects a magnetic resonance signal generated from the subject due to the application of the radio-frequency magnetic field, thereby creating an image. Such magnetic resonance imaging apparatus includes a gradient coil that adds spatial positional information to a magnetic resonance signal by applying a gradient magnetic field onto the subject.
The gradient coil is repeatedly supplied with a pulse current while imaging, thereby generating heat to a large extent. Especially in recent years, a speedup in switching of a gradient magnetic field and an enhancement of the strength of a gradient magnetic field are strongly required along with the speedup in an imaging technology, so that heat generation by a gradient coil becomes more marked.
Heat generation by a gradient magnetic field has a possibility of giving influence on the quality of a taken image, or giving a pain to a subject to be imaged. For this reason, for example, a technology of cooling a gradient coil while imaging by circulating a coolant through cooling pipes provided inside the gradient coil has been proposed (for example, see JP-A 2006-311957 (KOKAI).
However, the conventional technology described above has a problem that ends of a gradient coil cannot be cooled as described below.
FIG. 10 is a schematic diagram for explaining a problem of the conventional technology using cooling pipes. FIG. 10 depicts a state of the inside of one end of a gradient coil that is formed in a substantial drum shape. As shown in FIG. 10, for example, in a gradient coil 1, a cooling pipe 2 is provided so as to be introduced in a direction from one end toward the other end of the gradient coil 1, then to be bent toward the circumferential direction, and then to reach the other end by being wound in a spiral fashion along the drum shape of the gradient coil 1.
In such case, for example, as shown in FIG. 10, an area 3 surrounded by the cooling pipes immediately after the introduction and the cooling pipe in the first lap is formed at an end of the gradient coil 1. No cooling pipe is arranged in the area 3, so that it is not cooled with coolant. As a result, for example, among a plurality of iron shims arranged in the gradient coil 1 to correct ununiformity of a static magnetic field in the imaging zone, an iron shim 5 arranged at the end of the gradient coil 1 becomes not to be cooled.
According to the conventional technology, there is a case where a plurality of cooling pipes are wound in parallel with a gradient coil in order to improve the cooling efficiency of the gradient coil. In such case, a wider space is further required for bending the cooling pipes at an end of the gradient coil, so that an area not to be cooled becomes wider.